Article for use in an OCT-method and intraocular lens

ABSTRACT

An article for use in an OCT method, the article comprising a solid substrate and nanoparticles dispersed in or on the substrate in at least one light transmissive portion of the article such that the nanoparticles result in an increased extinction of the light transmissive portion along a transmission direction of the light transmissive portion compared to the substrate being free of nanoparticles. The extinction of the light transmissive portion along the transmission direction is less than 6, wherein the extinction is defined as a negative decadic logarithm of a ratio of an intensity of light which is transmitted through the light transmissive portion to an intensity of light which is incident on the light transmissive portion, wherein the light is in at least one of a visible and a near infrared wavelength range.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 61/234,778, filed Aug. 18, 2009, and entitled “Articlefor Use in an OCT-Method and Intraocular Lens,” and German PatentApplication No. 10 2009 037 708, filed Aug. 17, 2009, entitled“ERZEUGNIS ZUR VERWENDUNG IN EINEM OCT-VERFAHREN UND INTRAOKULARLINSE,”the contents of which are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to an article for use in an OCT method andan intraocular lens. The present invention further relates to a system,which comprises an OCT system and an article for use in an OCT methodand/or an intraocular lens. Furthermore, the present invention relatesto methods, in which optical coherence tomography (OCR) is applied byusing an article in an OCT method and/or an intraocular lens. Inparticular, the present invention relates to an article for use in anOCT method, wherein the article comprises a substrate, in whichnanoparticles are dispersed.

BACKGROUND OF THE INVENTION

Optical coherence tomography (OCT) is an optical method for determiningstructural information within a volume portion of an object.

Recently, surgical procedures are increasingly conducted by using OCT toimage the surgical area. For such surgical operations, which areconducted by using OCT, there are presently articles, like surgicalinstruments and implants available, which however are only of limitedpractical use. These articles are mostly manufactured of metal andtherefore structures of the examination area, which are locateddownstream of the article are covered by the article. Also, knownarticles for in vitro investigations (i.e. outside of a living organism)conducted by using OCT are only of limited practical use.

Today, OCT is widely applied in eye examination procedures. Inparticular, OCT may be applied during cataract surgery, in which thelens after being emulsified is removed from the capsular bag and anintraocular lens is implanted. However, it has shown that theintraocular lenses, which are presently available, are only of limiteduse for being observed by OCT.

Therefore, it is an object to provide an article, which is suitable foruse in an OCT method. A further object is to provide a system and amethod, which improves imaging of such an article by using OCT.

It is a further object to provide an intraocular lens which makes itpossible a more successful cataract surgery. A further object is toprovide a system and a method, which comprises or applies such anintraocular lens, wherein OCT is used for generating images.

SUMMARY OF THE INVENTION

According to an embodiment, there is provided an article for use in anOCT method, wherein the article comprises a solid substrate.Nanoparticles are dispersed in the substrate or are dispersed on thesubstrate, wherein the nanoparticles are located in a light transmissiveportion of the article, such that the nanoparticles result in anincreased extinction of the light transmissive portion along atransmission direction of the light transmissive portion compared to thesubstrate being free of nanoparticles. The extinction of the lighttransmissive portion along the transmission direction is less than 6, inparticular less than 5, further in particular less than 4, further inparticular less than 3, further in particular less than 2, wherein theextinction is defined as a negative decadic logarithm of a ratio of theintensity of light, which is transmitted through the light transmissiveportion of the article along the transmission direction to the intensityof light, which is incident on the article, wherein the light is in atleast one of the visible and near infrared wavelength range.

The substrate is made of a solid material. In other words, the substrateis in a non-liquid and non-gaseous state. The solid substrate may be aplastic and/or an elastic material. In particular, the substrate mayhave a hardness of at least 1 according to Mohs scale.

For example, the substrate may be made of at least one of glass,plastics, a polymer material, a synthetic thread.

The substrate, when being free of nanoparticles (i.e. when the substrateis measured without any nanoparticles), may have an extinction in thelight transmissive portion along the transmission direction of below 2,in particular of below 1, further in particular of below log₁₀2, whereinthe light is in at least one of the visible and near infrared wavelengthrange.

The extinction is a measure for a degree of attenuation of an intensityof light, which is transmitted trough the at least one lighttransmissive portion. The extinction of the intensity of light, which istransmitted through the at least one light transmissive portion may becaused by different physical processes. These physical processescomprise for example adsorption, scattering, fluorescence excitation,etc. Therefore, an increase of the extinction of a substrate may notnecessarily be coupled to an increase of the reflectivity of thesubstrate. For determining the extinction, light in at least one of thevisible and the near infrared wavelength range is directed onto the atleast one light transmissive portion of the article, along atransmission direction, and transmitted through the at least one lighttransmissive portion. After transmission of the light through the lighttransmissive portion, substantially along the transmission direction,the intensity of the light is determined. Thereafter, a ratio of thelight intensity, which is transmitted through the article to a lightintensity, which is incident on the article is determined.

The extinction is a property of the article, which is dependent inparticular on the transmission direction, the structure and materialalong the transmission direction within the at least one lighttransmissive portion of the article. Furthermore, the extinction alsodepends on a wave length of the used light. The extinction may beconsidered as an integral parameter along a path of the light, which istransmitted through the article along the transmission direction. Theintensity I_(t) of the transmitted light is related to the intensityI_(e) of the incident light according to Lambert's law:I _(t) =I _(e)·exp(−τ·D),  Equation (1)

wherein the parameter τ denotes the linear extinction coefficient in theat least one light transmissive portion of the article along thetransmission direction, and wherein D denotes a length of a path throughthe at least one light transmissive portion along the transmissiondirection. The extinction is given by the following equation:

$\begin{matrix}{{extinction} = {- {\log_{10}( \frac{I_{t}}{I_{e}} )}}} & {{Equation}\mspace{14mu}(2)}\end{matrix}$

Hence, the following equation results, being the relationship betweenthe extinction and the linear extinction coefficient τ:

$\begin{matrix}{{extinction} = {\frac{1}{\ln\; 10} \cdot \tau \cdot D}} & {{Equation}\mspace{14mu}(3)}\end{matrix}$

The extinction is measured by using light in the visible and/or nearinfrared wavelength range. The intensity I_(t) of the transmitted lightand the intensity I_(e) of the incident light are measured. Light in thevisible wavelength range comprises electromagnetic waves havingwavelengths of between 400 nm to 700 nm. Light in the near infraredwavelength range comprises electromagnetic wavelengths, which are longerthan 700 nm and range up to about 2.5 μm, in particular up to about 1.3μm. In one or more portions of the visible and near infrared wavelengthrange, the extinction may be below 6, in particular below 5, further inparticular below 4 or 3 in the at least one light transmissive portionof the article and along the transmission direction. The extinction doesnot have to be between these limits in all portions of the visible andnear infrared wavelength range.

In case the substrate being free of nanoparticles is transmitted bylight in the visible and/or near infrared wavelength range along alength D, which is parallel to the transmission direction, theextinction may be below log₁₀2. Hence, at least half of the intensity ofthe incident light is transmitted through the substrate in case thesubstrate comprises no or a negligibly small amount of nanoparticlesalong the path of the transmitted light. Thereby, the pure substrate issubstantially transparent for light in the visible and/or near infraredwavelength range.

The substrate may be considered as a basic structure or matrix whereinnanoparticles are dispersed in at least one light transmissive portion.The nanoparticles may be dispersed in a volume of the light transmissiveportion of the substrate and/or arranged on a surface of the substrate.The presence of the nanoparticles in the at least one light transmissiveportion results to an increased extinction in this portion, compared tothe same portion being void of nanoparticles (i.e. where only thesubstrate is present). The increase of extinction which is caused by thepresence of the nanoparticles may be calculated in particular from thearrangement of the nanoparticles and their properties. This is discussedfurther below. The increased extinction may assume a value of up to 5.In particular, the increased extinction may assume a value of up to 6.At the limit of 6 of the extinction, in the at least one transmissiveportion of the article, the ratio of the intensity of the transmittedlight to the incident light amounts to 10⁻⁶. Further in particular, theincreased extinction may assume a value of up to 4. The increasedextinction may also assume values of up to 3.

The substrate may have a hardness of at least 1 according to Mohs scale.The Mohs scale of hardness comprises degrees of hardness of 1 to 10 with1 being the softest and 10 the hardest. Specimen with a higher hardnessscratch other specimen with a lower Mohs hardness. One example of aspecimen with a Mohs hardness of 1 is talc, which can be scraped byfingernails. The substrate of the article may have a hardness of greaterthan 1, greater than 2, greater than 3 greater than 4, greater than 5,greater than 6 or greater than 7. The substrate is therefore no liquid,but a solid material, which is composed of elements or molecules in asubstantially stable configuration relative to each other.

According to an embodiment, a reflectivity in at least one reflectiveportion of the light transmissive portion is increased caused by thepresence of nanoparticles by at least 0.1%, in particular by at least1%, further in particular by at least 10%, further in particular by atleast 50%, further in particular by at least 100%, further in particularby at least 500%, further in particular by at least 5000%.

The term reflectivity may be a portion of light, which is reflected bythe reflective portion of the article in a direction, which issubstantially reverse to the direction of incidence on the article,wherein the direction of incidence is parallel to the transmissiondirection.

Hence, the reflected light, which contributes to the measurement of thereflectivity, propagates substantially in a direction reverse to thedirection of incidence, wherein the propagation direction of thereflected light may deviate from the reverse incidence direction by upto 10 degrees, in particular by up to 5 degrees, further in particularby up to 2 degrees. The increase in reflectivity by for example 10% inthe at least one portion compared to the substrate void of nanoparticlesis caused by the presence of nanoparticles. The increase of reflectivityin this portion preferably causes an increased signal in case the signalis imaged using an OCT system. Therefore, dispersing the nanoparticlesinto a volume or onto a surface of the substrate, the article which isimaged by OCT can be made visible.

According to an embodiment, the article comprises a reflective portionwithin the light transmissive portion, wherein a reflectivity of thereflective portion along the transmission direction is greater than10⁻¹⁰, in particular greater than 10⁻⁹, further in particular greaterthan 10⁻⁷ or greater than 10⁻⁶ or greater than 10⁻⁵ wherein the light isin at least one of the visible and near infrared wavelength range.

The wavelengths, which are used to define the extinction of the lighttransmissive portion of the article and the wavelengths, which are usedto define the reflectivity of the reflective portion of the article maybe at least in part identical.

The reflectivity of the reflective portion may be defined by thefollowing equation:

$\begin{matrix}{{reflectivity} = {( \frac{I_{r\;}}{I_{e}} ).}} & {{Equation}\mspace{14mu}(4)}\end{matrix}$wherein I_(e) is the intensity of the light, which is incident on thearticle, wherein the light is measured after it has left the OCT systemand before it enters the article. I_(r) is the intensity of light, whichis reflected by the reflective portion of the article, wherein theintensity is measured after the light has left the article and before itenters the OCT system.

The reflectivity is measured along the transmission direction of thelight transmissive portion. In other words, I_(e) is the intensity oflight of an incident light beam, which is parallel to the transmissiondirection and I_(r) is the intensity of the reflected light beam, whichis antiparallel (i.e. has an opposite direction) to the transmissiondirection.

The reflectivity of a reflective portion of the transmissive portion maybe measured by means of an OCT system. For example, by knowing thesensitivity of the OCT system, it may be possible to measure a value ofa reflectivity of a portion of an object, which has been scanned by theOCT measuring light. The sensitivity of an OCT system may be determinedfor example by theoretical calculations or by comparative measurements.

The reflectivity of the reflective portion is therefore a property ofthe article, which may be measured by scanning the reflective portionwith an OCT system.

In case the reflective portion is not located on the surface, thereflectivity of the reflective portion may also include the extinctionof the light, which is caused by traveling from the surface of thearticle to the reflective portion and further by traveling back to thesurface of the article after having been reflected at the reflectiveportion.

According to an embodiment, the nanoparticles which are dispersed in theat least one light transmissive portion, cause an increase in extinctionof at least 10⁻⁴ relative to the substrate when being free ofnanoparticles. In other words, the nanoparticles cause an increase by afactor of 10⁻⁴ relative tot the substrate when being free ofnanoparticles. In particular, the increase in extinction may be of atleast 10⁻³, further in particular of at least 10⁻², further inparticular of at least 10⁻¹.

The increased extinction may be accompanied for example by an increasedreflectivity, which facilitates a detection of the article by an OCTsystem.

According to an embodiment, the nanoparticles have an extent of between1 nm and 100 μm, in particular of between 2 nm and 500 nm, further inparticular of between 10 nm and 200 nm. The nanoparticles may haveshapes, such as substantially spherical, ellipsoidal, and therefore mayhave different diameters along different directions. The extent of ananoparticle may be defined as the greatest diameter, width or length ofthe nanoparticle. A minimal diameter of the nanoparticles may be in therange between 1 nm and 100 μm, in particular between 2 nm and 500 nm orbetween 10 nm and 200 nm. Nanoparticles of this extent are commerciallyavailable.

According to an embodiment, the nanoparticles are made of a material,which comprises a metal, in particular gold, silver, titanium, copper,cobalt, nickel, and/or iron; silicon and/or oxygen. In particular, themetal may be deposited on a shell, which surrounds a core, wherein thecore may comprise silicon. In other words, the nanoparticles maycomprise an inert metal, such as gold, which may be arranged on itssurface. Thereby, the nanoparticle may be biocompatible.

According to an embodiment, the nanoparticles may be dispersed in avolume region of the substrate, additionally or alternatively, thenanoparticles are dispersed on a surface region of the substrate.

In case the at least one portion, where nanoparticles are dispersed is avolume region, the concentration of the nanoparticles may be defined asthe number of nanoparticles in a unit volume of the volume regionarticle. In case the at least one light transmissive portion, in whichthe nanoparticles are dispersed is a surface region, the concentrationof the nanoparticles may be defined as the number of nanoparticles perunit surface area.

According to an embodiment, concentrations of nanoparticles in twosubportions of the portion, in which the nanoparticles are dispersed,differ by at least a factor of two.

Concentrations of nanoparticles may be greater in subportions having asmaller transmission path length, compared to subportions having alonger transmission path length, wherein the transmission path lengthsof the subportions are oriented parallel to the transmission direction.

According to an embodiment, the nanoparticles may be dispersed in avolume or on a surface of the article such that an article oftransmission path and concentration of nanoparticles is substantiallyconstant. Thereby, an article may be made visible by imaging with an OCTsystem, independent from its shape.

According to an embodiment, at least 80% of the nanoparticles arearranged on a surface of the substrate. Arranging the majority of thenanoparticles on the surface of the substrate makes it possible to imagethe surface of the substrate by an OCT system, wherein the surfacespatially limits the article. Such a spatially limiting surface andhence the surface of the article may therefore be better determined byan OCT-system, thereby enabling improved positioning of the articlewithin or close to an object, which is to be examined.

According to an embodiment, the extent of the at least one portion, inwhich the nanoparticles are dispersed, along at least one transmissiondirection of light is smaller than 20 mm, in particular smaller than 10mm, further in particular smaller than 2 mm. The extent of the at leastone portion, in which the nanoparticles are dispersed is denoted withthe symbol D.

According to an embodiment, the substrate is made of a material, whichcomprises glass and/or plastic, in particular a polymer. Thereby, thesubstrate may be manufactured in an easy way.

According to an embodiment, the article is a manipulator, in particulartweezers, scalpel, a tube, and additionally or alternatively an implant,in particular an intraocular lens or a surgical thread. The tweezers maycomprise jaws, which are movable relative to each other, such thattissue may be grasped by closing the jaws. The at least one portion, inwhich the nanoparticles are dispersed may be located at least partlywithin at least a grasping portion of the jaws. The scalpel may comprisea blade, which is arranged at the substrate. The tube may be designed assuction tube. The suctioning tube may be designed such that liquid issuctionable from an examining region or a surgical area.

According to an embodiment, the article comprises a surgical thread,comprising in particular Prolene having a thickness of less than 100 μm,in particular of less than 30 μm. Such a surgical thread may be used foreye surgery, in particular for a surgery, where the thread is insertedinto the Schlemm's canal of the human eye. By using an OCT system incombination with the surgical thread, it is possible to determine thegeometry of the Schlemm's canal when the surgical thread has beeninserted into the Schlemm's canal. Furthermore, by inserting the threadinto the Schlemm's canal, the Schlemm's canal can be extended in adefined way.

According to an embodiment, an article as described above is used in anOCT method for imaging the article. Due to an increased reflectivity ofthe article in the at least one light transmissive portion because ofthe presence of the nanoparticles, the article can better be imaged byan OCT system compared to commonly available articles.

According to an embodiment, a system is provided, having a light sourcefor emitting an OCT measuring light beam along a path of OCT measuringlight to an object and a detector for detecting the OCT measuring lightreturning from the object; and further comprising an article asdescribed above. The article is arrangeable in the path of the OCTmeasuring light. The light source may comprise light having wavelengthsin the visible and/or near infrared wavelength range, wherein abandwidth of the light source is configured such that a coherence lengthof the light emitted by the light source ranges between severalmicrometers and several ten micrometers. A part of the OCT measuringlight beam which is emitted from the light source is directed along apath of OCT light which may comprise mirrors, lenses and/or fiber opticsto an object. The light penetrates into the object along a penetrationdepth. A part of the penetrated measuring light is reflected within theobject depending on a reflectivity of the object. A second part of thelight, which is emitted by the light source is reflected at a referencesurface. The first part and the second part are interferometricallysuperposed. The superposed light is detected by a detector and convertedinto electrical signals, which represent intensities of the detectedsuperposed light. Due to the comparably short coherence length of theOCT measuring light, constructive interference can only be observed incase the difference of the optical path of the OCT measuring light whichtravels towards and returns from the object and the OCT measuring lightof the second part which is reflected by the reference surface is lessthan the coherence length of the OCT measuring light.

Different embodiments may comprise different variants of the OCT system.The different variants of the OCT system may be different in the way, inwhich structural information is scanned along a depth direction (axialdirection), and also in the way in which the superposed light isdetected. According to time domain OCT (TD-OCT), the reference surface,at which the second part of the light which is emitted by the lightsource is reflected, is displaced for obtaining structural informationof the object from different depths. In this case, an intensity of thesuperposed light may be detected by a photo detector.

Also in frequency-domain-OCT (FD-OCT), the second part of the OCTmeasuring light, which is emitted by the light source is reflected atthe reference surface. However, the reference surface does not have tobe displaced for obtaining structural information from different depthswithin the object. Rather, the superposed light is split by aspectrometer into spectral portions. The spectral portions may forexample be detected by a position sensitive detector. Structuralinformation of the object along the depth direction may be obtained by aFourier transform of the measured spectrum of the superposed light(Fourier domain OCT).

Another variant of FD-OCT is swept source OCT (SS-OCT). A spectrum ofsuperposed light is recorded successively, wherein a mean wavelength ofa narrow band of illumination light is varied continuously and, at thesame time, the superposed light is detected by using a photo diode.

The article, in which nanoparticles are dispersed in at least one lighttransmissive portion thereof is arrangeable in the OCT measuring lightand therefore imageable. Since the article may have in the lighttransmissive portion in which nanoparticles are dispersed an extinctionof less than 5, reflecting structures, which are located downstream ofthe article are imageable by an OCT system having a sensitivity of 100dB, wherein the light is transmitted through the article two times.

According to an embodiment, the extinction of the portion in whichnanoparticles are dispersed, is small enough, such that reflectingstructures are detectable, which are located downstream of the portionin which nanoparticles are dispersed. Thereby, by choosing the material,the geometrical shape, the extent and the concentration of thenanoparticles, the extinction of the portion in which nanoparticles aredispersed may be adjusted such that the portion in which thenanoparticles are dispersed and also the structures which are locateddownstream are imageable with the OCT system.

According to an embodiment, the following relationship holds between areflectivity of a reflective portion which is in the light transmissiveportion, and the sensitivity of the OCT system:−10*Log₁₀(reflectivity)<sensitivity,wherein the light is in at least one of the visible and the nearinfrared wavelength range.

According to an embodiment, the system further comprises a processingsystem for determining data, which represent a structure of the objectfrom the OCT measuring light, which is detected by the detector anddepending on the optical path along which the OCT measuring light hastraversed the article. An optical path through the article which istransmitted by light corresponds to a traveled path and an index ofrefraction n of the article in the light transmissive portion. The indexof refraction n of the article may be greater than 1. At lowconcentrations of the nanoparticles, the index of refraction of thearticle may be approximately the index of refraction of the substrate.In general, the index of refraction depends on the wavelength of the OCTmeasuring light. The index of refraction of vacuum is exactly 1 for eachof the used wavelengths. For solid materials, such as glass or plastics,the index of refraction for visible or near infrared light rangesbetween 1.2 and 1.9. The optical path of the OCT measuring light, alongwhich the light is transmitted through the article is therefore greaterthan the geometrical path through the article which is traversed bylight. For correcting the thereby generated artifacts to structuralinformation of portions, which are located downstream of the articlewhich is traversed by light, the measured position of the structures,which are imaged by the OCT system and which are located downstream ofthe article which is traversed by light are shifted by twice thedifference between the optical path through the article which istransmitted by light and the geometrical path through the article whichis transmitted by light. Thereby, corrected structure information of theobject is obtained.

According to an embodiment, there is provided a method, comprising:illuminating an object with an OCT measuring light along a path of OCTmeasuring light; arranging one of the above described articles in theOCT measuring light; detecting OCT measuring light returning from theobject and the article; and determining of data representing a structureof the object based on the detected OCT measuring light.

According to an embodiment, there is provided a method for manufacturingone of the above described articles, wherein the method comprisesgeometrically shaping a substrate and dispersing nanoparticles into oronto the substrate. When nanoparticles are arranged substantially on asurface of the article, the geometrically shaping of the substrate maybe performed before the nanoparticles are dispersed onto the substrate.The dispersing of nanoparticles onto the substrate may for example beperformed by dipping the substrate into a solution with nanoparticles,by spraying the nanoparticles onto the substrate or by evaporating thenanoparticles close to the substrate. When the nanoparticles are locatedwithin the volume of the article substantially in the at least oneportion in which the nanoparticles are dispersed, the dispersing of thenanoparticles in the substrate may be performed before the geometricalshaping of the substrate. In particular, the substrate may be in aliquid state, when the nanoparticles are dispersed therein. Thenanoparticles may be distributed homogeneously or inhomogeneously withinthe substrate.

According to an embodiment, there is provided an intraocular lens, whichcomprises: an optical element, which is substantially transparent in thevisible wavelength range; a mark which is arranged outside of theoptical element in a radial direction, wherein the mark compared to theoptical element has an increased reflectivity within the visible and/ornear infrared wavelength range in at least a portion thereof by at leasta factor of 2, in particular a factor of 10. The reflectivity of themark and the optical element may refer to incident light, which isbackscattered.

According to an embodiment, the reflectivity of the mark is at least10⁻¹⁰. The reflectivity of the mark may be measured with light in atleast one of the visible and infrared wavelength range. The reflectivitymay be further in particular at least 10⁻⁹, further in particular atleast 10⁻⁸, further in particular at least 10⁻⁷.

The mark is arranged outside the optical element in a radial direction,i.e. in a direction, which is oriented perpendicular to the opticalaxis. Thereby, the mark which may have a low transparency does not blockout light, which is transmitted through the optical element along theoptical axis. The higher reflectivity of the mark compared to theoptical element results in an improved imaging of the mark by the OCTsystem.

The mark may in particular comprise a reflector foil. The mark may bestructured such that it represents an identification of the opticalproperties of the intraocular lens, in particular of the opticalelement. For example, the mark may be structured such that the markcontains or comprises information which represents a refractive power ofthe spherical and/or toric optical element. A refractive power of atoric intraocular lens is intended to correct an astigmatic eye. In thisrespect, it is necessary that the intraocular lens is inserted into thecapsular bag in a correct orientation, i.e. azimuthal orientation intothe human eye for achieving a successful correction of the astigmatism.To this end, the toric intraocular lens comprises structures on itsmark, which make it possible to determine the direction of the principalaxis of the toric optical element like a lens. Thereby, a correctimplantation of the intraocular lens is facilitated for correctingHypermetropia, Myopia and/or astigmatism. Other information may be codedin the mark, such as a date of manufacturing of the intraocular lens, amaterial of the intraocular lens or the like.

The intraocular lens may be implantable at different positions withinthe eye, such as within the natural capsular bag, in the anterior eyechamber or in the posterior eye chamber.

According to an embodiment, the optical element has a positive opticalrefracting power in the visible wavelength range, in particular between+18 diopters and +22 diopters. Thereby, an intraocular lens may functionin particular as a substitute for a natural lens. When a bundle ofparallel light beams is transmitted through the optical element alongthe optical axis in the visible wavelength range, the light rays arerefracted towards the optical axis, such that light bundles which areparallel before being transmitted through the optical element aretransformed into a convergent light bundle. A ratio of a light intensitywhich is transmitted through the optical element to a light intensitywhich is incident onto the optical element in the visible wavelengthrange is greater than 70%, in particular greater than 90%,

The positive optical refracting power of the optical element may alsorange between +1 diopters and +8 diopters.

According to an embodiment, the optical element has a negative opticalrefracting power in the visible wavelength range, in particular rangingto −14 diopters.

The intraocular lens may be used as a phakic lens such as a posteriorchamber intraocular lens (implanted contact lens, ICL) which isimplanted between the iris and the natural lens in the sulcus or as ananterior chamber contact lens which is attached to the iris. For suchintraocular lenses, the optical element may have an optical refractivepower of less than 19 diopters or a negative refractive power.

According to an embodiment, the intraocular lens further comprises aholding element, which extends from inside to outside along a radialdirection for holding the intraocular lens within the capsular bag ofthe eye. A size of the holding element is adapted to the size of thecapsular bag. The holding element may in particular comprise two holdingarms, which are arranged exactly or substantially opposite to each otherand which extend from inside to outside along a radial direction,wherein the holding arms accommodate the optical element in a centralportion of the intraocular lens between those holding arms.

According to an embodiment, the mark is arranged at the holding element.Thereby, the holding element serves two functions, which simplifies theconstruction of the intraocular lens.

According to the embodiment, the mark is arranged at a radial distancefrom the optical axis of between 1 mm and 10 mm, in particular between 2mm and 7 mm, further in particular of between 3 mm and 6 mm. Thereby,the mark is arranged at a radial distance, which is greater than theradius of a maximal opening of the pupil of a human eye. Furthermore,the distance is smaller than the radius of the capsular bag of a humaneye. In particular, the mark is arranged at a radial distance from theoptical axis of the human eye such that the mark, when locateddownstream of the iris, may be imaged by an OCT system, withoutaffecting the field of view of the human eye.

According to an embodiment, the mark comprises nanoparticles.

According to an embodiment, the intraocular lens comprises an article asdescribed above for use in an OCT method, wherein the article has asubstrate having a hardness of at least 1 according to the Mohs scaleand an extinction of below log₁₀2, wherein nanoparticles are dispersedin the substrate in at least one light transmissive portion of thearticle, such that the nanoparticles result in an increased extinctionof below 5, in particular of below 6. The extinction is defined as anegative decadic logarithm of a ratio of the intensity of light which istransmitted through the article to light which is incident onto thearticle, wherein the light is in the visible or near infrared wavelengthrange.

According to an embodiment, there is provided a system, which comprises:an OCT system having a light source for emitting a beam of OCT measuringlight along a path of the OCT measuring light towards the object and adetector for detecting OCT measuring light which returns from theobject; and an intraocular lens, such as described above. Theintraocular lens is arrangeable in the path of OCT measuring light.Thereby, the intraocular lens, in particular the mark of the intraocularlens may be imaged by the OCT system.

In doing this, the intraocular lens may be implantable into the capsularbag for replacing the natural lens, or may be a posterior chamber lens,which may be fixed between the iris and the natural lens in the sulcusciliaris, which is a circular groove between the root of the iris andthe ciliary body. The intraocular lens may be fixed through a haptic ofthe intraocular lens.

According to an embodiment, there is provided a method, comprising:illuminating at least a portion of an eye with a beam of OCT measuringlight along a path of OCT measuring light; arranging a mark of anintraocular lens as described above in the path of OCT measuring light;detecting at least a part of the OCT measuring light, which returns fromthe eye and the mark; imaging of the mark and least a portion of the eyeby using the detected OCT measuring light.

The intraocular lens may be located within the capsular bag of the eyeor may be an anterior chamber intraocular lens or a posterior chamberintraocular lens. Thereby, the intraocular lens according to anembodiment may be imaged in a medical examination. The medicalexamination may be carried out solely for the purpose of obtaining theoptical properties of the intraocular lens by imaging the mark anddecoding of the coded information on the mark. A similar medicalexamination may be carried out before, during or after an eye surgery.Thereby, for example, the correctness of the optical properties of theintraocular lens, such as a refractive power, or a correct orientationof the intraocular lens may be confirmed.

According to an embodiment, the method further comprises determining alocation of the intraocular lens relative to the eye. The determining ofthe location of the intraocular lens relative to the eye may comprise adetermining of the orientation of the optical axis of the opticalelement of the intraocular lens relative to an orientation of theoptical axis of the human eye. Furthermore, in case the intraocular lensis also toric, the determining of the location of the intraocular lensrelative to the eye may comprise a determining of the azimuthalorientation of a main axis of the intraocular lens. The direction ofthis main axis may be obtained from the information which is comprisedby the mark of the intraocular lens.

BRIEF DESCRIPTION OF THE DRAWINGS

The forgoing as well as other advantageous features of the inventionwill be more apparent from the following detailed description ofexemplary embodiments of the invention with reference to theaccompanying drawings. It is noted that not all possible embodiments ofthe present invention necessarily exhibit each and every, or any, of theadvantages identified herein.

FIG. 1 illustrating an OCT system with an article and an intraocularlens according to an embodiment;

FIG. 2 illustrates an article which a suction tube according to anembodiment;

FIG. 3 illustrates an article in the form of tweezers according to anembodiment;

FIG. 4 illustrates an article, which is a scalpel according to anembodiment;

FIG. 5 a illustrates an article, which is a surgical thread according toan embodiment;

FIG. 5 b illustrates results of OCT measurements, which are obtained bymeasuring a surgical thread shown in FIG. 5 a;

FIG. 6 a shows an intraocular lens according to an embodiment;

FIG. 6 b shows an intraocular lens according to an embodiment;

FIG. 7 a shows results of OCT measurements according to an exemplaryembodiment of a method;

FIG. 7 b shows results of OCT measurements according to an exemplaryembodiment of a method; and

FIG. 7 c shows results of OCT measurements according to an exemplaryembodiment of a method.

DETAILED DESCRIPTION OF THE INVENTION

In the exemplary embodiments described below, components that are alikein function and structure are designated as far as possible by alikereference numerals. Therefore, to understand the features of theindividual components of a specific embodiment, the descriptions ofother embodiments and of the summary of the invention should be referredto.

FIG. 1 schematically illustrates, in a simplified representation, an OCTsystem 1, which is used for examination of an human eye 2. Inparticular, the OCT system 1 may be used during an eye surgery, inparticular during a cataract surgery. In the embodiment, which isschematically illustrated in FIG. 1, the OCT system is a Fourier domainOCT system (FD-OCT system), which is also referred to as spectral domainOCT system. Further embodiments comprise a swept source OCT system(SS-OCT system) or a time domain OCT system (TD-OCT system).

The FD-OCT system 1 comprises a light source 3, which generatesmeasuring light 5 of a certain spectrum. The light source 3 comprises asuper luminescent diode, which is designed such that OCT measuring light5 is generated having a spectrum with a mean wavelength and a spectralwidth. The mean wavelength is about 1000 nm and has a spectral width of20 to 30 nm. Alternatively, instead of using a super luminescent diode,the light source 3 may comprise a white light source and spectralfilters, which are arranged in the path of OCT measuring light forapproximately providing the above described spectrum. Through theoptical fiber 4, the OCT measuring light 5 which is generated by thelight source 3 is guided to the divider/coupler 7. The fiber opticdivider/coupler 7 is configured such that OCT measuring light 5 isdivided into two light portions 9 and 15. Light portion 9 is guided to areflecting reference surface 11 by an optical fiber 4, at which thelight portion 9 is reflected to constitute the light portion 9′. Thereference surface 11 is disposable in directions which are indicated bydouble arrow 12. Thereby, a path length, which is traveled by lightportions 9 and 9′ is variable.

The other light portion 15 of the OCT measuring light 5 is guided by anoptical fiber 4 to a scanner 8 having an illumination optical system.The scanner 8 including the illumination optical system is designed suchthat a focused beam of OCT measuring light 16 is formed having a definedcross-sectional extent in the examination area (i.e. an object region)of about 10 to 50 μm. The scanner 8 having the illumination opticalsystem may also be designed such that a beam of measuring light 16 isformed, which consists of parallel light beams, in particular, forinvestigating a posterior portion of the eye, such as the retina.

The scanner 8 including the illumination optical system is furtherdesigned such that the bundle of OCT measuring light 16 is laterallyguided over the examination area of the human eye 2. For this purpose,the scanner 8 may comprise one or more mirrors, which are pivotableabout different axes.

The bundle of OCT measuring light 16 interacts with structures of thehuman eye 2, such as the cornea 13, the iris 14, the capsular bag 17,the intraocular lens 19, in particular the mark 20 of the intraocularlens 19, and with the suction tube 21. The suction inlet 21′ of thesuction tube 21 is arranged close to the capsular bag 17. Theinteraction of the bundle of OCT measuring light 16 comprises differentphysical processes such as scattering, reflection and absorption. Aportion of the incident bundle of OCT measuring light 16 is reflectedinto a substantially reverse direction (i.e. reverse to the direction ofthe incident light), captured by the scanner 8 and directed again intothe optical fiber 4 as light 16′.

The light 16′ carries structure information of the examination area ofthe eye into which the bundle of OCT measuring light 16 has beenpenetrated. Light 16′ is guided to the fiber optic divider/coupler 7,where it is superposed on the light portion 9′, which has been reflectedat the reference surface 11. Thereby, superposed light 25 is formed. Thesuperposed light 25 is guided via the optical fiber 4 to thespectrometer 27. The spectrometer 27 comprises a dispersion device 29for spectrally dispersing the superposed light into spatially separatedlight portions 30. Each of the light portions 30 comprises light waveshaving wavelengths of a certain wavelength range. The wavelength rangesof different light portions may be different. The spatially separatedlight portions 30 are detected by a position sensitive detector 31,which comprises a plurality of pixels for separately detectingintensities of different spatially separated light portions 30 and forgenerating electrical signals.

The electrical signals are led via signal line 39 to a control andprocessing system 33, which is designed such that the electrical signalsare processed and data representing a structure of the examination areaof the eye are determined. Namely, the intensities of the detectedspectral light portions 30 represent a spectrum of the superposed light25. From the spectrum of superposed light 25, structure informationalong a depth direction 23 is determinable after having appliedbackground subtraction, spectral resampling and determining of a Fouriertransform. The control and processing system 33 may be designed suchthat via a signal line 35, a change in the characteristics of the lightsource 3 in view of its spectrum is controlled. The control andprocessing unit may further be designed such that via a signal line 37,a dispersion strength of a dispersion device 29 is varied. From datawhich represents the structure of the examination area of the eye 2, animage of the examination area of the eye 2 may be obtained, which may bedisplayed on a monitor (not illustrated). This representation maycomprise for example a volumetric view or a cross-sectional view of theobject.

Embodiments provide articles, which may be applied during an examinationor a surgery in which an OCT system 1 is used. On the one hand, thearticles have a suitable reflectivity for being imaged by the OCT system1, on the other hand, the bundle of OCT measuring light 16 is attenuatedby the extinction of the article only such that anatomical structures ofthe eye 2 which are located downstream of the article are detectable andhence imageable by the OCT system 1.

The suction tube 21, which is illustrated in FIG. 1, comprisesnanoparticles which are disposed on its surface. Thereby, the signal ofthe suction tube 21 is increased which leads to an improved detection bythe OCT system 1 compared to a suction tube 21 without any disposednanoparticles. The suction tube 21 is comprised by a suction device 22,which is provided for suctioning off an emulsified natural lens from thecapsular bag 17 during a cataract surgery. The suction device 22 may bedesigned in the form of a phaco handpiece for phacoemulsification.Thereby, a suctioning off of lens fragments may be performed in anintegrated way with the phaco handpiece.

The surgeon approaches the suction device 22 and in particular thesuction inlet 21′ of the suction tube 21 to the location where thesurgery is performed. Thereby, the suction inlet 21′ is approached asclose as possible to an incision, which is made at the capsular bag 17for suctioning off an emulsified natural lens. The increase in contrastof the imaged suction tube 21 which is caused by the dispersednanoparticles provides a facilitated positioning of the suction inlet21′ of the suction tube 21 for the surgeon.

FIG. 2 schematically illustrates in more detail a portion of the suctiontube 21 during an examination of the eye 2 by using the OCT system 1.The suction tube comprises a cylindrical substrate body having adiameter A of 2 mm and a wall thickness of about ⅕ mm. The diameter Amay also have values of between 1 mm and 3 mm, and the wall thicknessmay also have values of between 1/20 mm to ½ mm. The cylindricalsubstrate body is made of glass or plastics. On the outer surface of thesubstrate body, there are located nanoparticles 26 which have asubstantially constant surface concentration, i.e. the number ofnanoparticles per unit area is substantially constant on the outersurface of the cylindrical substrate body. The nanoparticles have beendeposited by dipping the substrate body into a solution of nanoparticleshaving a concentration of about 7×10⁸ nanoparticles per ml. In otherembodiments of the suction tube, the nanoparticles 26 are not onlydeposited on the surface of the substrate body, but rather are alsolocated in the bulk of the cylindrical substrate body. Alternatively oradditionally, the nanoparticles 26 may be deposited on the cylindricalinner surface of the suction tube 21.

During examination of the eye 2, the suction tube 21 is arranged in abeam path of the bundle of measuring light 16 of the OCT system 1, whichis illustrated in FIG. 1. An intensity of the bundle of OCT measuringlight 16, which is incident on the suction tube 21, is denoted as I_(e).An intensity of the bundle of OCT measuring light, which transmits thesuction tube 21 is denoted as I_(t). Because of the presence of thenanoparticles on the surface of the cylindrical substrate body of thesuction tube 21, the intensity I_(t) of the transmitted OCT measuringlight is smaller than the intensity I_(e) of the incident OCT measuringlight. The extinction, which is defined in equation (2) above may assumevalues of up to 10. Notwithstanding this significant attenuation of theintensity of the bundle of OCT measuring light 16 after having beentransmitted through the suction tube 21, an anatomical structure of theeye 2, which is located downstream of the suction tube 21, (in this casethe capsular bag 17) is imageable by the OCT system 1 illustrated inFIG. 1 because of the high sensitivity of the OCT system 1.

Generally, the sensitivity of an OCT system is defined as the minimalreflectivity of the probe arm of the interferometer at which the signalto noise ration is 1. Instead of determining the minimal reflectivity ofthe probe arm, the maximum attenuation or extinction of the bundle ofOCT measuring light at which an ideal mirror is detectable by anintensity I_(t) of OCT measuring light. This results in the sensitivitywhich is given in decibel

$\begin{matrix}{{sensitivity} = {{{- 10} \cdot \log}\; 10( \frac{I_{t}}{I_{e}} )}} & {{Equation}\mspace{14mu}(5)}\end{matrix}$

Sensitivities of modern OCT systems have been investigated in thepublication “Performance of Fourier domain vs. time domain opticalcoherence tomography”, R. Leitgeb et al, Optics Express, Vol. 11, No. 8,pages 889 to 894. It is possible to obtain a sensitivity of up to 108dB. Using equations (2) and (5) and taking into account that the pathgoes through the article two times, and structures which are locateddownstream of the article have to be detectable, the maximum extinctionis given by:

$\begin{matrix}{{\max.\mspace{14mu}{extinction}} = {\frac{1}{2} \cdot \frac{1}{10} \cdot {sensitivity}}} & {{Equation}\mspace{14mu}(6)}\end{matrix}$

Thereby, in case the extinction of the suction tube 21 along atransmission direction, which is given by the direction of the incidentbundle of OCT measuring light 16, is smaller than the maximumextinction, which is defined in equation (6), in particular smaller than5, a boundary layer or interface of the capsular bag 17 is detectable bythe OCT system 1.

OCT measuring light 16′, which emanates from the examination area of theeye 2, which is located downstream of the suction tube 21, has coveredan additional optical path D·(n−n_(M)). D denotes a thickness of thetransmitted substrate material of the suction tube 21 having an index ofrefraction n on the way to and fro, and n_(M) represents an index ofrefraction of the medium, which is in this case the aqueous humor withinthe eye. Without a correction of structural data taking intoconsideration this additional optical path, the capsular bag 17 would beillustrated according to the dashed line 17′.

The control and processing system 33, however, is designed such thatbased on knowledge of the geometry of the suction tube 21, therefractive index of the suction tube 21 and the orientation and positionof the suction tube 21, a correction is performed. Thereby, the capsularbag 17 which is erroneously depicted downstream of the suction tube 21as contour 17′, is displayed as corrected contour 17. This correctionmay be performed in a real space of the volume data set, for example bydisplacing pixel values according to the additional optical path of theOCT measuring light 16, 16′ for portions of the object, which arelocated downstream of the suction tube 21.

Embodiments of an article, may have an index of refraction, which isadapted to a medium of the area of examination. In this case acorrection as described above is not required. For example, the articlemay be made of plastics, having an index of refraction of about 1.3 to1.4 in the wavelength range of the used OCT measuring light. A deviationof the index of refraction of the article from a mean index ofrefraction of the medium of the area of examination may be chosen to besmaller than the ratio of the resolution of the OCT system to the extentof the article of the portion through which the OCT light istransmitted.

FIG. 3 shows a further article 41, which may be used in a method byusing the OCT system 1. The article is configured as tweezers made ofglass or plastics. Nanoparticles 26 are dispersed in the volume.

Different embodiments of the article which are described in thisapplication may comprise different nanoparticles or a mixture ofdifferent nanoparticles. The nanoparticles may comprise for exampleAlO₃, wherein the nanoparticles have an extent of between 100 nm and 100μm. The nanoparticles may also comprise Au, wherein the nanoparticleshave an extent of between 2 nm to 250 nm. The nanoparticles may alsocomprise Ag, wherein the nanoparticles have an extent of between 20 nmto 80 nm or of between 20 nm and 300 nm. Additionally or alternatively,the nanoparticles may comprise other metals and/or silicon. Thenanoparticles may consist completely of metal or may comprise a coremade of silicon or silicon oxide around which a shell of metal isformed. For given articles having a given geometry and a given substratematerial, the extinction along any transmission direction of the articlemay be calculated depending on a material, a shape, a size and aconcentration of nanoparticles. In the calculation, the nanoparticle maybe approximated by a sphere.

Since the scattering process of light at a homogeneous sphere can not beexpressed analytically, numerical procedures such as Mie theory have tobe applied for a given configuration of the article. The so-called Miecoefficients a_(n) and b_(n) are calculated for a given configuration ofthe article and given boundary conditions, for example by applying theprogram “MieCalc” (Bernhard Michel) and/or “Mie Scattering Calculator”(Scott Prahl). Based on these Mie coefficients and based on the radiusof the sphere of the nanoparticles, the efficiency of the extinctionQ_(ext) may be calculated for a given article. The calculation of theMie coefficients is also based on the complex index of refractionn=n_(r)−i·n_(i) of the nanoparticles. By way of example, at a wavelengthof 840 nm of the OCT measuring light, gold nanoparticles have a realindex of refraction n_(r)=0.18 and an imaginary index of refractionn_(e)=5.36. The linear coefficient of extinction τ is related to theefficiency of extinction Q_(ext) by the following equation:τ=π·r ² ·Q _(ext) ·n _(d)  Equation (7)

Herein, r denotes the radius of the nanoparticle, Q_(ext) denotes theefficiency of extinction and n_(d) denotes the density of thenanoparticles in the article; in particular in the portion of thearticle, which is transmitted by light. After the efficiency ofextinction Q_(ext) has been calculated based on the infinite seriesaccording to the Mie theory, the efficiency of extinction τ may beobtained; and by using equation (3) the extinction of the article may beobtained in the at least one light transmissive portion, in whichnanoparticles are dispersed. The extinction therefore linearly dependson the path D, through which light has been transmitted through thearticle. For nanoparticles, which are made of gold, which have aconcentration of n_(d)=7.0·10⁸/ml and a radius of r=100 nm and furtherin case of a given sensitivity of 108 decibel (dB) of the OCT system 1,a maximum extent D of the article in the light transmissive portion inwhich the nanoparticles are dispersed of D_(max)=32 cm results.According to equation (7) above in combination with equation (3) above,at a density, which is 10 times higher, i.e. n_(d)=7.0·10⁹/ml, a valueof D_(max)=3.2 cm results.

Based on this description, the person skilled in the art is able todetermine from a given sensitivity of the OCT system, a given geometryof the article, some or all of the relevant properties of thenanoparticles, such as material, extent, concentration, etc. such thatequation (6) is fulfilled. Thereby, structures of the area ofexamination, which are located downstream of the article and in the beampath of the bundle of OCT measuring light 16, are detectable by the OCTsystem 1.

Furthermore, based on the size, structure and/or concentration of theparticles, characteristics of backscattering of the nanoparticles may bedetermined by using suitable calculations. Thereby, by adapting theparameters of the nanoparticles, a higher reflectivity of thenanoparticles may be achieved for an improved detection by the OCTsystem.

The tweezers 41 comprise two legs 41 a and 41 b which can be movedtowards and away from each other, such that teeth which are located inthe jaws 42 a and 42 b may grab and hold tissue by applying a pressingforce. The legs 41 a and 41 b comprise glass or plastics as a substrateand nanoparticles 26 which are dispersed in the volume having aconcentration of about n_(d)=7.0·10⁸/ml. In a method for using thetweezers 41 and by applying the OCT system 1, which is illustrated inFIG. 1, the tweezers 41 are imaged and the spatial orientation andposition relative to the surrounding tissue of the eye 2 is determined.Thereafter, a correction of structure information which representanatomical structures which are located downstream of the tweezers 41 isapplied, in analogy to the correction method which has been describedreferring to FIG. 2.

The tweezers, which are schematically illustrated in FIG. 3 may be usedfor epiretinal membrane peeling. Tissue of the retina, is peeled byusing the tweezers, wherein an accurate positioning of the tweezers inrelation to the epiretinal membrane is possible by imaging with the OCTsystem. In particular, a distance between the tweezers and theepiretinal membrane may be determined by using the OCT system.

FIG. 4 illustrates a further embodiment of an article 43, which is usedin a method which makes use of the OCT system 1. The article 43 isconfigured as a surgical scalpel, which comprises a metal plate 44 in aportion 43 a. The substrate body of the scalpel 43 is made of atransparent material like plastics or glass and comprises a section 43 ahaving a smaller cross-sectional extend D₁ and a section 43 b having agreater cross-sectional extent D₂. In the substrate body of the scalpel43, nanoparticles are distributed, having a higher concentration in thesection 43 a than in the section 43 b. The inhomogeneous concentrationof the nanoparticles 26 in the sections 43 a and 43 b is chosen suchthat an extinction along a transmission direction defined by thedirection of the bundle of OCT measuring light 16 in the section 43 a issubstantially equal to an extinction in the portion 43 b. Thereby, it isensured, that an intensity I_(t,a) of OCT measuring light 16, which istransmitted through the section 43 a is substantially equal to anintensity I_(t) of OCT measuring light 16, which is transmitted throughthe section 43 b, i.e. I_(t,b)=I_(t,a). Thereby, structures of the eye2, which are located downstream of the scalpel 43 may be imagedsubstantially with the same signal to noise ratio, independent of aposition along a direction of longitudinal extent, which is in this caseapproximately perpendicular to the transmission direction of the scalpel43.

FIG. 5 a schematically shows a further embodiment 45 of the article,which may be used in combination with the OCT system 1, which isillustrated in FIG. 1. The article 45 is a surgical thread, which may beinserted into the Schlemm's canal 47 of a human eye during an eyesurgery. The surgical thread may in particular be used in combinationwith the method of viscocanaloplasty, wherein a liquid is injected forextending the Schlemm's canal.

The Schlemm's canal, which is limited in the cross-sectional view ofFIG. 1 by lines 47 a and 47 b, and which is denoted in FIG. 1 byreference sign 47, contributes to the fluid regulation of the anteriorchamber of the eye between the iris and the cornea. During an eyesurgery, the tread 45 may be inserted into the Schlemm's canal 47, 47 a,47 b. Thereby, either the geometry of the Schlemm's canal, which isotherwise only difficult to be imaged, may be determined or theSchlemm's canal may be deformed in a suitable way, for example bystretching. For increasing the contrast of the image generated by theOCT system 1, the surgical thread 45, which is made of a material suchas Prolene comprises nanoparticles 26 which are deposited on the surfaceof the surgical thread by dipping the thread of Prolene into a solutionof nanoparticles having a concentration of 7·10⁸ nanoparticles per ml.The thread of Prolene 45 has a cross-sectional diameter of about 30 μm.

FIG. 5 b illustrates results of two OCT measurements, wherein in theupper portion, there is shown a thread of Prolene without nanoparticlesand in the lower portion, there is shown tread of Prolene withnanoparticles as described above, wherein the thread of Prolene isimaged by an OCT system 1 as shown in FIG. 1. The upper image 48 of thethread of Prolene without nanoparticles shows a lower signal which makesit difficult to obtain an accurate image of the thread for determiningits position. In contrast thereto, the lower image of the thread ofProlene, in which nanoparticles are dispersed, has a signal which ishigher by a factor of four than in the upper image 48. Thereby a moreaccurate measurement or a more definite manipulation of the Schlemm'scanal during an eye surgery is possible by using an OCT system.

Other articles according to embodiments comprise portions of surfaces,which are provided with one or more layers which increase a reflectivityor which are roughened through a process, for increasing theimageability of the surfaces by an OCT system.

FIGS. 6 a and 6 b schematically illustrate in a top view embodiments ofan intraocular lens. The intraocular lens 19 a, which is shown in FIG. 6a comprises an optical element 50 a, which is substantially transparentin the visible wavelength range. The optical element 50 a has a positiverefractive power and an optical axis 50 a, which is perpendicular to thedrawing layer. The optical element 50 a may be a spherical and/or toriclens.

Furthermore, the intraocular lens 19 a comprises two holding elements 52a and 53 a, which extend from inside to outside in a radial directionand which serve to hold the intraocular lens 19 a in the capsular bag 17of the human eye 2. At the holding element 52 a, there is provided amark 54 a and at the holding element 53 a, there is provided a mark 55a. The mark 54 a or 55 a may for example comprise a reflecting foiland/or information on optical properties of the intraocular lens 19 a,treatment data, patient data and the like. The mark 54 a or 55 a may forexample comprise characters or a barcode and information about analignment of the main axis of the optical elements 50 a in case it is atoric optical element.

The optical element 50 a has a radius r₀ which defines a circular area,in which the optical power of the optical element 50 a has a positiverefractive power. The marks 54 a and 55 a are located outside of thecircular area defined by the radius r₀, in a portion between the radiir₁ and r₂. The radii r₁ and r₂ are chosen under consideration of theanatomy of the eye 2 which is to be examined. In particular, it has tobe ensured, that the intraocular lens 19, which is inserted into thecapsular bag 17 is held within the capsular bag 17 by the holdingelements 52 a and 53 a and further that the marks 54 a and 55 a arelocated along an optical axis of the eye behind (i.e. downstream) of theiris, without limiting the field of view of the eye. For example, r₁ maybe chosen to be greater or equal to 3 mm and r₂ may be chosen to besmaller or equal to 6 mm.

The intraocular lens 19 a may be used for an improved cataract surgeryby using the OCT system 1, which is illustrated in FIG. 1. Thereby, thehigh sensitivity of the OCT system 1 may be used for imaging marks 54 a,55 a of the implanted intraocular lens 19 a, which is located in thecapsular bag 17 behind the iris 14, whereby it is possible to determinethe exact position of the intraocular lens 19 a within the capsular bag17. An inaccurate position or inaccurate orientation of the implantedintraocular lens 19 a may be determined, for example a tilt of theoptical axis 51 a of the intraocular lens 19 a in relation to an opticalaxis of the eye or an inaccurate azimuthal orientation of theintraocular lens 19 a relative to the optical axis 51 a in case theoptical element 50 a is a toric optical element, the orientation ofwhich is given by a main axis. An accurate positioning of an intraocularlens has been difficult by using common imaging systems and commonintraocular lenses.

FIG. 6 b illustrates a further embodiment 19 b of an intraocular lens.Such as the intraocular lens 19 a, which is illustrated in FIG. 6 a, theintraocular lens 19 b, which is illustrated in FIG. 6 b comprises anoptical element 50 b having an optical axis 51 b and two holdingelements, which are located outside of the optical element 50 b in aradial direction for holding the intraocular lens 19 b in the capsularbag of a human eye 2. Contrary to the intraocular lens 19 a, which isillustrated in FIG. 6 a, there are provided no marks on the holdingelements 52 b and 53 b. Instead, a mark 54 b is provided on an outwardlydirected portion 56, wherein the outwardly directed portion 56 extendsin a direction from inside to outside of the optical element 50 b in aradial direction. Other embodiments of intraocular lenses comprisefurther marks on the holding elements or further supporting elements,such as outwardly directed portions. The marks may comprisenanoparticles, which are arranged within a volume or a surface of acorresponding supporting element.

In addition to the articles as described above, other commonly useditems or items which are necessary in a surgery may be provided withnanoparticles, such as visco elastic materials, rinsing liquids,catheters or the like. Liquids, which contain nanoparticles, may be usedto increase the contrast after having been injected into a tissue whichis examined during being imaged by an OCT system. Liquids containingnanoparticles, such as visco-elastic materials may for example beinjected into the anterior chamber of the eye or posterior chamber ofthe eye or into the Schlemm's canal for increasing contrast.

FIGS. 7 a, 7 b and 7 c illustrate the use of a liquid, which containsnanoparticles for increasing the contrast of the image of the anteriorchamber of a trout's eye by using an OCT system. FIG. 7 a shows an imageobtained by an OCT system, which is illustrated in FIG. 1, of a trout'seye, wherein in the image which is inserted in the lower left corner,the eye of the trout is shown in top view. The image in FIG. 7 a of thenatural eye of a trout shows the outer limit of the cornea as a line 13,whereas the anterior chamber of the eye which is located below seems tohave no limiting structures below the cornea.

FIG. 7 b shows an image of the same eye of the trout shortly after aninjection of a liquid, which contains nanoparticles, below the cornea.Portions within the anterior chamber of the eye, which are enriched withthe liquid which contains nanoparticles, show an increased OCT signal.

FIG. 7 c shows an increased OCT signal after a short time of waiting ina band 58 below the cornea 13, which is generated by reflection of theOCT measuring light at the nanoparticles. The fact that the liquid whichcontains nanoparticles has only spread out within a limited band,indicates that the anterior chamber of the eye is limited by structuresbelow the cornea 13, which has not been recognizable in images of thenatural eye of the trout. Thereby, using liquids containingnanoparticles which are injected into a tissue to be examined, animproved examination of this tissue is made possible.

An injected liquid which contains nanoparticles may be used togetherwith articles according to FIGS. 2 to 5 a and FIGS. 6 a and 6 b duringan examination by an OCT system. Thereby, examinations and surgeries mayfurther be improved.

While the invention has been described with respect to certain exemplaryembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, the exemplary embodiments of the invention set forth hereinare intended to be illustrative and not limiting in any way. Variouschanges may be made without departing from the spirit and scope of thepresent invention as defined in the following claims.

What is claimed is:
 1. A lens comprising: an optical element, having anoptical axis, wherein the optical element is substantially transparentin a visible wavelength range; a mark, which is spaced apart from theoptical element in a radial direction of the optical element, wherein aportion of the mark has an increased reflectivity of at least a factorof 2 compared to the optical element, in at least one of the visible anda near infrared wavelength range; wherein the lens is an intraocularlens.
 2. The lens according to claim 1 wherein the reflectivity of themark is at least 10⁻¹⁰ .
 3. The lens according to claim 1 furthercomprising: a holding element extending from inside to outside of thelens in the radial direction of the optical element for holding the lenswithin a capsular bag, wherein the mark is arranged at the holdingelement.
 4. The lens according to claim 1 wherein the mark is arrangedat a radial distance of between 1 mm and 10 mm from the optical axis. 5.The lens according to claim 1 wherein the mark comprises nanoparticles.6. A system comprising: an OCT system having a light source for emittinga beam of OCT measuring light along a path of OCT measuring lightleading to the object and a detector for detecting a portion of the OCTmeasuring light returning from the object; an lens, comprising: anoptical element having an optical axis, wherein the optical element issubstantially transparent in a visible wavelength range; a mark, whichis spaced apart from the optical element in a radial direction of theoptical element, wherein a portion of the mark has an increasedreflectivity of at least a factor of 2 compared to the optical element,in at least one of the visible and a near infrared wavelength range,wherein the lens is an intraocular lens and is arrangeable in the pathof the OCT measuring light.
 7. A method comprising: illuminating atleast a portion of an eye with a beam of the OCT measuring light along apath of OCT measuring light; arranging a mark of a lens in the path ofthe OCT measuring light, wherein the lens is an intraocular lens andcomprises: an optical element having an optical axis, wherein theoptical element is substantially transparent in a visible wavelengthrange; wherein the mark, is spaced apart from the optical element in aradial direction of the optical element, wherein a portion of the markhas an increased reflectivity of at least a factor of 2 compared to theoptical element, in at least one of the visible and a near infraredwavelength range, wherein the method further comprises: detecting aportion of the OCT measuring light returning from at least a portion ofthe eye and the portion of the mark; and imaging the portion of the markand the portion of the eye by using the detected portoin of the OCTmeasuring light.
 8. The lens according to claim 1, wherein the opticalelement has a positive optical refractive power.
 9. The lens accordingto claim 1, wherein the optical element has a negative opticalrefractive power in the visible wavelength range.
 10. An intraocularlens comprising: an optical element, having an optical axis, wherein theoptical element is substantially transparent in a visible wavelengthrange; a mark, which is spaced apart from the optical element in aradial direction of the optical element, wherein a portion of the markhas an increased reflectivity of at least a factor of 2 compared to theoptical element, in at least one of the visible and a near infraredwavelength range; wherein the intraocular lens comprises an article,wherein the article comprises: a solid substrate, at least one lighttransmissive portion, having a transmission direction, nanoparticles,which are at least one of dispersed in and dispersed on the substrate inat least one light transmissive portion; wherein the nanoparticles areconfigured and dispersed such that the nanoparticles result in anincreased extinction of the light transmissive portion in thetransmission direction compared to the substrate being free of thenanoparticles, wherein the extinction of the light transmissive portionin the transmission direction is less than 6, wherein the extinction isdefined as a negative decadic logarithm of a ratio of an intensity oflight which is transmitted through the light transmissive portion to anintensity of light which is incident on the light transmissive portion,wherein the light is in at least one of the visible and the nearinfrared wavelength range.
 11. The intraocular lens according to claim10, further comprising: a holding element extending from inside tooutside of the intraocular lens in the radial direction of the opticalelement for holding the intraocular lens within a capsular bag, whereinthe mark is arranged at the holding element.
 12. The intraocular lensaccording to claim 10, wherein the article comprises a reflectiveportion within the light transmissive portion, wherein a reflectivity ofthe reflective portion along the transmission direction is greater than10⁻¹⁰; and wherein the light is in at least one of a visible and a nearinfrared wavelength range.
 13. The lens according to claim 1, whereinthe mark is structured such that the mark contains information.
 14. Thelens according to claim 1, wherein the mark contains information, whichis related to at least one of optical properties of the lens, treatmentdata, patient data, a date of manufacturing of the lens, and a materialof the lens.
 15. The lens according to claim 1, wherein the markcomprises at least one of a barcode and a character.
 16. The lensaccording to claim 1, wherein the mark contains information whichrepresents at least one of a refractive power and a direction of aprincipal axis of the optical element.
 17. The lens according to claim1, wherein the mark comprises a reflecting foil.
 18. The methodaccording to claim 7, wherein the mark is structured such that the markcontains information; wherein the method further comprises obtaining theinformation by the imaging of the portion of the mark.
 19. The methodaccording to claim 7, wherein the mark contains information, which isrelated to at least one of optical properties of the lens, treatmentdata, patient data, a date of manufacturing of the lens, and a materialof the lens.
 20. The method according to claim 7, wherein the markcomprises at least one of a barcode and a character.
 21. The methodaccording to claim 7, wherein the mark comprises a reflecting foil. 22.The method according to claim 7, further comprising: determining anarrangement of the lens relative to the eye by the imaging of theportion of the mark.
 23. The method according to claim 7, furthercomprising: wherein the mark contains information which represents atleast one of a refractive power and a direction of a principal axis ofthe optical element; and wherein the method comprises determining the atleast one of the refractive power and the direction of the principalaxis by the imaging of the portion of the mark.
 24. The system accordingto claim 6, wherein the mark is structured such that the mark containsinformation.
 25. The system according to claim 22; wherein the system isconfigured to obtain the information by imaging the mark with the OCTsystem.
 26. The system according to claim 6, wherein the mark containsinformation, which is related to at least one of optical properties ofthe lens, treatment data, patient data, a date of manufacturing of thelens, and a material of the lens.
 27. The system according to claim 6,wherein the mark comprises at least one of a barcode and a character.28. The system according to claim 6, wherein the mark containsinformation which represents at least one of a refractive power and adirection of a principal axis of the optical element.
 29. The systemaccording to claim 6, wherein the mark comprises a reflecting foil. 30.The system according to claim 6, wherein the system is configured toimage the mark by using the the OCT system; and to determine anarrangement of the lens relative to an eye by the imaging of the mark.31. The system according to claim 6, wherein the lens further comprises:a holding element extending from inside to outside of the lens in theradial direction of the optical element for holding the lens within acapsular bag, wherein the mark is arranged at the holding element. 32.The system according to claim 7, wherein the mark comprisesnanoparticles.